Herbicidal compositions containing bipyridylium salts with reduced corrosiveness toward metals

ABSTRACT

Herbicidal compositions of bipyridylium diquaternary salts and a dithiophosphorous acid derivative. Examples of such derivatives are the salts of alkyl esters of dithiophosphoric acid.

United States Patent HERBICIDAL COMPOSITIONS CONTAINING BIPYRIDYLIUM SALTS WITH REDUCED CORROSIVENESS TOWARD METALS 6 Claims, No Drawings U.S.C1 M 71/94, 252/395 Int. Cl AOln 9/22 Field of Search 71/87, 94;

References Cited UNITED STATES PATENTS 2/1956 Mu11en,.1r.eta1 .6 252/395 2,841,486 7/1958 Osborn et a1. 71/87 2,989,392 6/1961 Baker l. 71/87 3,004,996 10/1961 Arakelian ct al. 252/395 3.156,551 11/1964 Brian 71/94 3,228,960 1/1966 Rigterink v. 71/87 3.238148 3/1966 Rauhut 71/87 3,340.041 9/1967 Homer etal 71/94 3,332,959 7/1967 Braunho1t'1. 71/74 3.347.790 10/1967 Meinhardtm. 4. 260/963 3,361 668 1/1968 Wiesc 260/963 3,396,183 8/1968 Brasch 7. 260/963 OTHER REFERENCES State Sci.-Res. etc; Protecting Ferrous & Nonferrous Metals etc.. (1965) CA64 p. 410 1966) Teubel et 31., Basic Heavy-duty Lubricant for Diesel Engines, (1965) CA 65 p. 3650 1966) Primary Examiner Lewis Gotts Aisislan! Examiner-G Hollrah Almrney Cushman, Darby and Cushman HERBICIDAL COMPOSITIONS CONTAINING BIPYRIDYLIUM SALTS WITH REDUCED CORROSIVENESS TOWARD METALS This invention relates to herbicidal compositions containing herbicidal bipyridylium quaternary salts together with a corrosion inhibitor, and to a process for inhibiting the corrosion of metals by herbicidal bipyridylium salts. Herbicidal bipyridylium quaternary salts have been disclosed in U.K. specifications 813,531 and 813,532. As disclosed in U.K. specifications 1,086,937, solutions of these compounds are somewhat Corrosive toward metals. Aluminum metal and its alloys are particularly rapidly attacked. The chloride and bromide salts, which are preferred from the point of view of cost and of convenience in manufacture, are among the more corrosive salts formed from bipyridylium quaternary cations. It has now been discovered the corrosion of metals by solutions of bipyridylium salts can be prevented or reduced by the incorporation of certain phosphorus acid derivatives into the solutions.

According to the present invention there is provided at herbicidal composition comprising a herbicidal bipyridylium diquaternary salt and a phosphorus acid derivative of the formula where R is an alkyl group of from one to 18 carbon atoms, R is an alkyl group offrom one to four carbon atoms or an alkoxy group offrom one to 18 carbon atoms, and M is a cation.

Examples of suitable cations include hydrogen ion (1-1") alkali metal ion (for example, Na), alkaline earth metal ion (for example /2Mg""), and ammonium ion of the formula (N R R R R in which R;,, R R and R each represent a hydrogen atom or an alkyl group (e.g. of 1-4 carbon atoms).

Examples of herbicidal bipyridylium salts include the following:

l,l-ethylene-2,2'-bipyridylium dibromide (diquat dibromide) 1,1 -dimethyl-4,4bipyridylium dichloride (paraquat dichloride) l,l '-bis-3 ,5-dimethylmorpholinocarbonylmethyl4,4'- bipyridylium dichloride (morfamquat dichloride) 1,1 '-di-2-hydroxyethyl4,4-bipyridylium dichloride l-(2-hydroxyethyl)-1'-methyl-4,4-biphridylium dichloride 1,1 -di-carbamoylmethyl-4,4'bipyridylium dichloride l,l -di-N-methylcarbamoylmethyl-4,4'-bipyridylium dichloride l, l -bis-N,N-dimethylcarbamoylmethyl-4,4'-bipyridylium dichloride 1,1 -bis-N,N-diethylcarbamoylmethyl-4,4'-bipyridylium dichloride 1,1 -diacytonyl-4,4-bipyridylium dichloride l,l -diethoxycarbonylmethyl-4,4-bipyridylium dibromide l,l '-diallyl-4,4'-bipyridylium dichloride The names in brackets set against the first three compounds in the above list are alternative names for these compounds in which the systemic chemical name for the cationic part of the compound has been replaced by the accepted common name for this entity. The bipyridylium salts listed above are all chlorides or bromides, in which form they are most commonly encountered, but a wide range of other salts is also possible, for example those having iodide, phosphate, sulfate nitrate, methylsulfate, thiocyanate, cyanate, borate, bromate, perchlorate, acetate, oxalate, citrate, benzoate, phenylacetate, or succinate anions. Any desired salt may be used, since the herbicidal activity of the bipyridylium salts is inherent in the cation and is independent of the nature of the anion.

Preferred compositions according to the invention are those which contain a phosphorus acid derivative of the above formula in which R, is an alkyl group and R is an alkoxy group, and in which the total number of carbon atoms in R and R together is from eight to 14 carbon atoms.

A particularly preferred composition is that which contains a phosphorus acid derivative of the above formula in which R. is an amyl radical and R, is an amyloxy radical.

Further preferred compositions are those which contain a phosphorus acid derivative of the above formula in which R is an alkyl group of from five to 12 carbon atoms and R is a methyl group.

Compositions according to the invention may be solid or liquid. Solid compositions may contain for example, an inorganic salt as a diluent. Although solid compositions may be dry and relatively noncorrosive when freshly prepared, it is nevertheless desirable to incorporate a corrosion inhibitor, since the compositions may absorb moisture on storage and in any case are usually diluted with water before use. Liquid compositions may comprise, for example, a solution or dispersion of the bipyridylium salt in water containing a surface-active agent. Preferred surface-active agents are those which are nonionic. These include the condensation products of p octyl and p-nonylphenol with ethylene oxide, for example the condensation product of p'nonylphenol with from seven to eight molar proportions of ethylene oxide sold under the name LIS- SAPOL (LISSAPOL" is a trade mark). Other examples of nonionic surface-active agents include the condensation products of ethylene oxide with mixtures of primary amines derived from coconut oil or soyabean oil fatty acids, for example those sold under the name ETHOMEEN ("ETHOMEEN" is a trade mark). Still further examples of nonionic surface-active agents include the N-oxides of condensation products of ethylene oxide with cocoamine, for example those sold under the name AROMOX C15 (AROMOX is a trade mark).

Conveniently, the amount of the phosphorus acid derivative used in the compositions of the invention is from 0.01 to 10 percent of the weight of bipyridylium cation present. Preferably, the phosphorus acid derivative is used in an amount of from 0.5 to 5 percent by weight of the bipyridylium cation present in the composition.

In another aspect the invention provides a process of inhibiting the corrosion of metals coming into contact with herbicidal bipyridylium quaternary salts, by mixing the herbicidal bipyridylium quaternary salt with a phosphorus acid derivative ofthe above formula, in which R is an alkyl group of from one to 18 carbon atoms, R is an alkyl group of from one to four carbon atoms, or an alkoxy group of from one to 18 carbon atoms, and M* is a cation.

Compositions according to the invention are obtained by mixing the herbicidal bipyridylium salt with the phosphorus acid derivative, further components of the composition being either present initially or added later as desired. In the case of an aqueous composition the pH of the solution may be adjusted to near pH7 if desired, although the phosphorus acid derivatives prevent or reduce corrosion over a wide range of pH values.

The invention is illustrated by the following examples.

EXAMPLE 1 This example illustrates the effectiveness of salts of certain 0,0-dialkyl esters of dithiophosphoric acids in reducing corrosion of aluminum by a solution of paraquat dichloride.

Test solutions were made up, having the following compositions:

(The water contained sufficient sodium hydroxide to bring the initial pH of the solution within the range 6.5 to 7.5.)

For comparison, a control solution was prepared of the same composition except that the inhibitor was omitted. For the test, strips of British Standard 2L72 alloy were used This comprises a composite of an aluminum alloy coated on each side with aluminum metal to a thickness of 5 percent of the alloy center. The overall thickness of the composite sheet was approximately 0.028 inch, and the composition of the central alloy portion was as follows:

Component 3% by weight Copper 4 4 Magnesium 0.7

Silicon 0.7 Manganese 0.6 Aluminum to l% Strips of the aluminum alloy were immersed in the test solutions for 24 hours. Corrosion was assessed by determining the loss in weight of the strips. The results are given in table I below.

TABLE I Weight loss of aluminum strip (mg./ cmJ/day Inhibitor EXAMPLE 2 This example illustrates the degree of inhibition of corrosion obtained using various concentrations of corrosion inhibitor in a solution of paraquat chloride. The test solutions were made up as in example 1 except for the variation in the concentration of the corrosion inhibitor. and the corrosion test was carried out as in example l. Results are given in table 2 below TABLE 2 Weight loss Inhibitor of aluminum I concentration strip tmg Inhibitor (percent) cmJ/day) \one t'IitlIl'Ol solution) |o (I130 s li. til 0 l 1.11m is m Salllt :lS above 0. l u 3 U0 0. 5 U ()3 itllogt'li Uul L3 'lIi/AH \u uiiie as above U. i i. Do U. 5 (J. 3

i 5 ll. 3

EXAMPLE 3 This example illustrates the effectiveness of salts of certain O-alkyl monoesters of methylphosphonothiolothionic acid in reducing corrosion of aluminum by a solution of paraquat dichloride. The aluminum was in the form of strips of the alloy used in examples 1 and 2. Test solutions were prepared having the following compositions.

Purnquat dichloride (calculated as cation. It); Sodium acetate "X Sodium benzoate 5% Inhibitor 0 5% Water to I007:

The water contained suft'icicnt sodium hydroxide to bring the initial pH of the solution within the range 6.5 to 7.5.)

For comparison a control solution was prepared having the same composition except that the inhibitor was omitted. Corrosion was determied as in example l. The results are given in table 3 below:

This example illustrates the effectiveness of sodium diamyldithiophosphate.

in reducing corrosion of aluminum coated alloy sheets by paraquat dichloride solution over a range of pH values.

The aluminum alloy was the same as that used in example 1. Test solutions were prepared as follows Paraqual dichloride (calculated as cation; ltii Sodium acetate i it Sodium benzoatc 1 5'1 Sodium diamyltiithinphiisphute I) V} Water (containing varying amounts of sodium hydroxidei (u IOO'K' A series of solutions containing the above ingredients and ranging in pH from 3.5 to 9 5 in steps of 0.5 pH unit was prepared Corrosion assessment was carried out as in example I, and it was found that the weight loss of the aluminum alloy in these solutions was 0 5:0 25 milligrams/cm /day over the pH range 3 5 to 9 8 EXAMPLE 5 This example illustrates the effectiveness of sodium diamyldithiophosphate in reducing corrosion of aluminum alloy by paraquat diacetatc. A test solution was prepared as follows: 100% Paraquat diacelatc (calculated as cation) l; Sodium acetate L; Sodluni hcn/oatc I5; Sodium diamyldithiophosphatc 0.5; Water to lllU /l A control solution was prepared having the same composition except that the inhibitor was omitted. The aluminum alloy used was the same as that in example I. Corrosion was determined as in example l. The weight loss of the aluminum alloy in the solution containing no inhibitor was 6.2 milligrams/cm. /day, while the weight loss of the aluminum alloy in the solution containing sodium diamyldithiophosphate was 05 milligrams/cmF/day.

tion. A test solution was prepared having the following composition:

Diquat dichloride (calculated as cation) IOk Sodium acetate 1.5% Sodium benzoate L5; Sodium diamyldithiophosphatc O 5'71 Water to Hit);

EXAMPLE 7 This example illustrates an aqueous composition, according to the invention, comprising a herbicidal bipyridylium salt and a phosphorus acid derivative.

Component Percentage by weight Paraquat dichloride (calculated as cation) Sodium acetate Sodium benzoate AROMOX C (AROMOX is a Trade Mark) Sodium diamyldithiophosphatc SILCOLAPSE antifoaming agent (SILCOLAPSE is a Trade Mark) Water to I00 EXAMPLE 8 This example illustrates an aqueous composition according to the invention, comprising a herbicidal bipyridylium salt and a phosphorus acid derivative.

Component Pcrccnlagc by weight Paraquat dichlonde {calculated a.\

cation) Sodium acetate Sodium hcn/oatc AROMCM (l5 (AROMOX is a Trade Mark) 2 Compound 3 of table 3 0.5 SILCOLAPSE antil'oamlng agent (SILCOLAPSE is a Trade Mark) 0,05 1 atcr to lUlJ What is claimed is:

l. A herbicidal composition of reduced corrosiveness toward metals in the presence of moisture comprising a her bicidal bipyridylium diquaternary salt and a corrosion inhibiting amount of l a phosphorus ingredient which consists essentially ofa phosphorus acid derivative of the formula wherein R, is an alkyl group of from one to 18 carbon atoms, R is selected from alkyl groups of from one to four carbon atoms or alkoxy groups of from one to 18 carbon atoms, and M is a cation selected from the group consisting of hydrogen ion, alkali metal ion, alkaline earth metal ion, and ammonium ion of the formula (N R:, R R R,;,* R R and R are selected from hydrogen or alkyl groups ofone to four car bon atoms (2) a minor'amount of sodium acetate and sodium benzoate and an inert carrier therefor, said composition containing a herbicidally effective amount of said bipyridylium salt.

2. A herbicidal composition according to claim 1 in which the group R of the phosphorus acid derivative is an alkoxy group and the total number of carbon atoms in R, and R together is from eight to 14,

3. A herbicidal composition according to claim 1 in which the group R, of the phosphorus acid derivative is an amyl radical and the group R is an amyloxy radical.

4. A herbicidal composition according to claim I in which the group R, of the phosphorus acid derivative is an alkyl group of from five to 12 carbon atoms inclusive, and R a methyl group.

5. A herbicidal composition according to claim 1 in which 0.5 to 5 percent by weight of the bipyridylium cation in the composition. 

2. A herbicidal composition according to claim 1 in which the group R2 of the phosphorus acid derivative is an alkoxy group and the total number of carbon atoms in R1 and R2 together is from eight to
 14. 3. A herbicidal composition according to claim 1 in which the group R1 of the phosphorus acid derivative is an amyl radical and the group R2 is an amyloxy radical.
 4. A herbicidal composition according to claim 1 in which the group R1 of the phosphorus acid derivative is an alkyl group of from five to 12 carbon atoms inclusive, and R2 a methyl group.
 5. A herbicidal composition according to claim 1 in which the phosphorus acid derivative is present to the extent of from 0.01 to 15 percent by weight of the bipyridylium cation in the composition.
 6. A herbicidal composition according to claim 1 in which the phosphorus acid derivative is present to the extent of from 0.5 to 5 percent by weight of the bipyridylium cation in the composition. 